sounds peculiar that the steering in the N20s would differ btwn the S and Xdrives. Electric Power Steering is only advertised for the x35 X1 on the BMW USA site, so I'm still holding hope that the Sdrive will also have hydraulic.
The reason Servotronic is standard in the x35 is because it's mostly software and almost free to implement. Servotronic has been standard on recent BMW hydraulic systems so I'm not sure why they are charging for it as an option now. Perhaps they are phasing this part out and it's more costly to purchase smaller quantities. Also not sure why they are offering hydraulic at all if they electric is more efficient. Don't get me wrong, but from a business perspective there must be something driving the persistance of hydraulic. Perhaps EPS is marginally more expensive and they still have hydraulic parts to consume. The E84 was developed with hydraulic, so it's a no brainer to continue if it makes sense for them financially. Maybe they are saving the boost in fuel economy for the next model year. I bet all E84 X1 steering will go electric before the model comes to an end.